4-31 The temperature of a gas stream is to be measured by a thermocouple whose junction can be approximated as a 1.2-mm-diameter sphere. The properties of the junction are k 35 W/m K, p = 8500kg/m3, and c, = 320 J/kg-K, and the heat transfer coefficient between the junction and the gas is h = 110 W/m2-K. Determine how long it will take for the thermocouple to read 99 percent of the initialtemperature difference.Answer: 22.8 s

The characteristics length of the thermocouple is,

Answered: 4-31 The temperature of a gas stream is…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

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An ordinary egg can be approximated as a 5.5-cm-diameter sphere whose thermal conductivity of roughly W overall density of p= 1000. mk' kg m² and heat capacity of Cp = 3000; kgk k = 0.6- : The egg is initially at a uniform temperature of T₁ = 10°C and is dropped into boiling water at T = 90°C Taking the convective heat transfer coefficient to be h = 10. - determine how long it will take for the egg to W m²K reach T = 70°C. In solving this problem, please use the One-term approximation model to compute the time needed by the center of the egg and the surface of the egg to reach the desired temperature of 70 C Please discuss the difference between the three results. In solving the problem, please follow the steps below. For the One-term approximation: 1. Compute the Biot number, use the egg radius (not the diameter) as the characteristic length T-Too 2. Compute the non-dimensional excess temperature 0 = Ti-Too 3. Look up in the table the values for A₁ and ₁ for the Biot number found…
Write the heat rate equation only, don’t evaluate. Using table 4.1 in “Introduction to Heat transfer, 6th ed., Wiley”
Q5Two large containers A and B of the same size are filled with different fluids. The fluids in containers A and B are maintainedat 0° C and 100° C, respectively. A small metal bar, whose initial temperature is 100° C, is lowered into container A. After1 minute the temperature of the bar is 90° C. After 2 minutes the bar is removed and instantly transferred to the othercontainer. After 1 minute in container B, the temperature of the bar rises 10°. How long, measured from the start of theentire process, will it take the bar to reach 99.9° C?
3- A building wall consists of 25 cm concrete (K= 1.75 W/m.K) and 1.9 cm plaster (K= 87 W/m.K) on the inside surface. The outside temperature is -18°C, while the room is held at 23.5°C DBT and 16.8°C WBT. (a) What is the temperature on the inside wall surface. (b) Will the moisture condense on the wall. (c) How many layers of 1.25 cm thick fiber-board insulation (K= 0.048 W/m.K) should be applied on the inside wall surface to prevent moisture to condense on it.
16-26 In a certain experiment, cylindrical samples of diameter 4 cm and length 7 cm are used (see Fig. 16–9). The two thermocouples in each sample are placed 3 cm apart. After initial transients, the electric heater is observed to draw 0.6 A at 110 V, and both differential thermometers read a temperature difference of 8°C. Determine the thermal con- ductivity of the sample. Answer: 98.5 W/m.K
A food product with 82% moisture content is being frozen. Estimate the specific heat of the product at -8°C when 82% of the water is in a frozen state. The specific heat of dry product solid is 2.5 kJ/(kg °C). Assume specific heat of water at -10°C is similar to specific heat of water at 0°C.
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A 30-cm-radius metallic sphere is having thermal conductivity of k = 100. overall density of W 7 mk p = 1500- kg m² and heat capacity of C₂ = 3000 The sphere is initially at a uniform temperature of kgk CO T₁ = 20°C and is dropped into boiling water at T = 90°C. The convective heat transfer coefficient is assumed to be only h = 50; W m²K Using lump model, compute the temperature of the sphere after t = 1200 seconds. In solving this problem, please use and show the following steps (do not use EES) 1. Compute the volume and surface area 2. Compute the characteristic length Lc = k p Cp h Lc 4. Compute the Biot number Bi k 5. Calculate the Fourier number Fo= (at)/Lc² 6. Calculate the excess temperature using 0 = exp(-Bi * Fo) T-Too 7. Compute the target temperature T using 0 = Ti-Too 3. Compute the diffusivity a = = the sphere Vol Vol As == 3 r³ and А¸ = 4πr²
3-18E Consider an electrically heated brick house (k = 0.40 Btu/h ft-°F) whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varies. On a certain day, the temperature of the inner surface of the walls is measured to be at 55°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h. Determine the amount of heat lost from the house that day. Also determine the cost of that heat loss to the homeowner for an electricity price of $0.09/kWh. FIGURE P3-18E 9 ft TiD=70°F 50 ft 35 ft
A large home ice cream maker is being used to freeze ice cream. The bowl is at -15C, having just been removed from the freezer. If the bowl is 0.6 m in diameter, the ice cream mix fills the bowl to a depth of 0.55 m, the convective heat transfer coefficient is 220 W/m2 K, and the amount of heat transferred from the ice cream mix to the bowl is 4,300 W, what is the temperature of the ice cream mix?
Answer this ASAP The diameter of the tube is 25 mm. The specific heat of water is 4.18 kJ/kg.°C. The overall heat transfer coefficient is 0.7 kW/m².°C. 1. Schematic of temperature distribution 2.ΔTLMTD 3.Actual heat transfer rate 4.Cmin 5.Maximum heat transfer rate

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